The invention relates generally to semiconductor fabrication and, in particular, to methods of fabricating an electrical fuse and device structures for an electrical fuse.
Programmable devices, such as electrical fuses (efuses) and antifuses, are fundamental elements that are widely being used in various programmable integrated circuits such as redundancy circuits of dynamic random access memories and static random access memories, programmable logic devices (PLDs), I/O circuits, chip identification circuits, etc. Electrical fuses may also constitute an element of a built-in self-repair system for a chip that constantly monitors a chip's functionality. If needed, the self-repair system can automatically activate one or more electrical fuses to respond to changing conditions.
The electrical fuse is electrically connected to one or more circuits and is initially closed at the time of fabrication. Conventional electrical fuses include two large plates defining an anode and a cathode, as well as a long, narrow fuse link connecting the anode and cathode. Electrical fuses may be dynamically programmed in real time by passing an electrical current of relatively high density through the fuse link. Large programming currents may cause the fuse link to rupture by an abrupt temperature increase and permanently open. Alternatively, smaller programming currents may cause a controlled electromigration of the fuse link material. Both programming modes elevate the resistance of the programmed electrical fuse in comparison with intact electrical fuses.
Although existing electrical fuses have proven adequate for their intended purpose, there exists a need for an improved structure for an electrical fuse and improved methods of manufacturing electrical fuses.